Blue organic electroluminescent devices having a non-hole-blocking layer
View Patent ↗An organic electroluminescent device includes an anode; a hole-transporting layer disposed over the anode; a light-emitting layer disposed over the hole-transporting layer for producing blue light in response to hole-electron recombination, wherein the light emitting layer includes at least one host material and at least one dopant material; a non-hole-blocking buffer layer formed in contact with the light-emitting layer, wherein the non-hole-blocking buffer layer has substantially the same ionization potential and the same electron affinity as those of one of the host materials in the light-emitting layer; an electron-transporting layer disposed over the non-hole-blocking buffer layer; and a cathode disposed over the electron-transporting layer.
1. An organic blue light-emitting electroluminescent device comprising:
a) an anode;
b) a hole-transporting layer disposed over the anode;
c) a light-emitting layer disposed over the hole-transporting layer for producing blue light in response to hole-electron recombination, wherein the light emitting layer includes at least one host material and at least one dopant material;
d) an undoped non-hole-blocking buffer layer formed in contact with the light-emitting layer, wherein the non-hole-blocking buffer layer has the same ionization potential and the same electron affinity as those of one of the host materials in the light-emitting layer;
e) an electron-transporting layer disposed over the non-hole-blocking buffer layer; and
f) a cathode disposed over the electron-transporting layer.
2. The organic blue light-emitting electroluminescent device of claim 1 wherein the electron energy band gap of the host material in the light-emitting layer is higher than 2.9 eV.
3. The organic electroluminescent device of claim 1 wherein the emission wavelength from the light-emitting layer is shorter than 490 nm.
4. The organic blue light-emitting electroluminescent device of claim 1 wherein the electron energy band gap of the non-hole-blocking buffer layer is higher than 2.9 eV.
5. The organic blue light-emitting electroluminescent device of claim 1 wherein the thickness range of the light-emitting layer is from 5 nin to 30 nm.
6. The organic blue light-emitting electroluminescent device of claim 1 wherein the thickness range of the non-hole-blocking buffer layer is from 5 nm to 30 nm.
7. The organic blue light-emitting electroluminescent device of claim 1 wherein the thickness range of the non-hole-blocking buffer layer is from 5 nm to 20 nm.
8. The organic blue light-emitting electroluminescent device of claim 1 wherein the host material in the light-emitting layer includes anthracene derivatives.
9. The organic blue light-emitting electroluminescent device of claim 8 wherein the anthracene derivatives include 2-(1,1-dimethyethyl)-9,10-bis(2-naphthalenyl) anthracene (TBADN) and 9,10-di-(2-naphthyl) anthracene (ADN).
10. The organic blue light-emitting electroluminescent device of claim 1 wherein the non-hole-blocking buffer layer is the same material as one of the host materials in the light-emitting layer.
11. The organic blue light-emitting electroluminescent device of claim 1 wherein the non-hole-blocking buffer layer includes a material selected from anthracene derivatives.
12. The organic blue light-emitting electroluminescent device of claim 11 wherein the anthracene derivatives include 2-(1,1-dimethyethyl)-9, 10-bis(2-naphthalenyl) anthracene (TBADN) and 9,10-di-(2-naphthyl) anthracene (ADN).
13. The organic blue light-emitting electroluminescent device of claim 1 wherein the non-hole-blocking buffer layer includes a material selected from blue emitting metal chelated oxinoid compounds.
14. The organic blue light-emitting electroluminescent device of claim 13 wherein the blue emitting metal chelated oxinoid compounds include Bis(2-methyl-8-quinolinolato)(4-phenylphenolato)aluminum (B-Alq).